This application is directed generally to the valve arts, and more particularly to a novel and improved type of rotary valve structure useful over a broad range of applications.
Many and varied applications require controllable valve arrangements for various purposes. For example, in material distribution systems, such as on-the-road or off-the-road spreader and sprayer apparatus, control valves for controlling the distribution of material must be accurately controlled from the operator's cab of the vehicle. Examples of such material distribution apparatus are agricultural fertilizer sprayer and/or spreaders, as well as machines used in agriculture for distributing various insecticides, herbicides, and other materials. It will be appreciated that such materials may be in either liquid or granular form.
Similarly, over-the-road vehicles may be utilized variously to spray liquid materials or spread granular materials for purposes such as dust control, for providing binder materials for some road surfaces, and for various ice control products. All of these applications require that some control arrangement be provided to control the flow of material to a distribution device, which may be a spray bar having one or more nozzles for spraying liquid materials, or a rotary broadcast type spreader or other spreader for distributing granular materials.
Such a control arrangement valve may employ a control valve in line with the supply of liquid to be sprayed at the nozzles, or in a return line. if desired, to control the pressure and/or flow at the nozzles. Alternatively, this control valve may be used as a control valve in a hydraulic or other control system for controlling the speed of one or more pumps, drive motors for conveyors, or other devices for delivering the liquid or granular material to the nozzles or other spreader apparatus for distribution.
In any of the foregoing applications, it is desirable to provide a valve which is capable of controlling flow over a relatively broad range, and has relatively fast response time to control signals applied thereto, while maintaining relatively high resolution. The ability to provide a wide range of valve openings from fully closed to fully opened must be coupled with a relatively high degree of resolution, in order to maintain accurate control over a broad range of desired material delivery rates. The ability to respond relatively quickly to control signals is important in order to both initially achieve and therafter maintain a desired distribution rate, since the speed of the vehicle distributing the material may vary considerably during spraying or spreading. Preferably, and especially in the case of some fertilizer materials, such as anhydrous ammonia, it is important that the valve be positively seated when in a closed position so as to positively seal against leakage of such materials when the distribution apparatus is not in operation. However, such a valve must also have a relatively low initial inertia or initial required torque, to assure relatively rapid response for quick start-up at a desired distribution rate.
While it is often desirable to provide for relatively small incremental changes in the degree of valve opening in such a control valve, it is also desirable in some instances to provide for rather great, and rapidly achievable incremental amounts of opening. The former is generally true at the low end or initial portion of the opening of a control valve, while the latter generally applies to the later or subsequent portion of opening prior to reaching the fully opened position.
The novel and improved valve of the invention substantially meets the foregoing requirements, while advantageously being relatively simple and inexpensive in its manufacture and design.
Briefly, and in accordance with the foregoing considerations, a novel and improved rotary valve comprises a valve body and a valve seat defining an orifice, said valve body being rotatable relative to said valve seat for selectively seating and unseating relative thereto and movable through a continuous range of intermediate positions between a valve closed position wherein the orifice is fully covered by the valve body and a valve fully open position wherein the orifice is substantially entirely free of the valve body; wherein said valve body comprises a substantially solid body defining a surface of complementary form for engaging said valve seat, and having a pivot axis about which said valve body is rotatably mounted relative to said valve orifice, a periphery of said valve surface defining at least first and second curvilinear surfaces having axes of curvature which extend substantially parallel with each other and with the pivot axis of the valve body; the axis of curvature of a first of said curvilinear surfaces being disposed inwardly of the said first surface and within the periphery of the valve body; and the axis of curvature of the second of said curvilinear surfaces being disposed on the opposite side of the said second curvilinear surface and outside of the periphery of the valve body, and a remaining portion of said valve body surface defining a cross-sectional area at least as great as the cross-sectional area of the valve orifice for fully covering the same when in the valve closed position; said first and second curvilinear surfaces following sequentially from said remaining surface and being oriented such that during rotation of the valve body about its pivot axis, the first surface will initially come into registry with said valve orifice for initially relatively slowly opening the valve, and thereafter said second surface will come into registry with said valve orifice for thereafter relatively rapidly opening said valve.